Electric storage batteries typically comprise an electrochemically active cell element comprising a plurality of interleaved positive and negative polarity electrode plates separated one from the other by thin, ribbed, microporous polymer (e.g., polyethylene, PVC, etc.) sheets interjacent adjacent plates. The separators serve to separate and electrically isolate one (e.g., positive electrode) from the other (e.g., negative counterelectrode), have sufficiently small pores therein to suppress interplate dendrite growth, and sufficiently high porosity as to permit electrolyte and ionic mobility within the cell. A commercially popular such separator comprises microporous polyethylene which is marketed under the tradenames DARAMIC.RTM. by the W. R. Grace Co. or RHINOHIDE.RTM. by the Emark Co. Typically, such separators will vary in thickness from about 0.006 in. to about 0.015 in. in the backweb section of the separator that lies between spacer ribs on the face of the separator. Some manufacturers envelop the plates of one or both polarities in individual sheaths or envelopes formed from sheets of the separator material. Enveloping the plates in separator sheaths reduces the possibility of interplate shorting occurring at the edges of adjacent positive and negative plates. A typical such sheath is formed by folding an elongated strip of separator material in half, transverse its length, and inserting the plate into the fold (see FIG. 1). Thereafter, the lateral edges of the sheath outboard the edges of the inserted plate are bonded together as by heat sealing, electrosonic welding, pressure welding or the like.
The electrode plates themselves typically comprise a conductive metal grid (e.g., lead) embedded in a mass of electrochemically active material (e.g., Pb or PbO.sub.2). One such grid comprises an expanded metal grid such as disclosed in U.S. Pat. No. 3,853,626 issued Dec. 10, 1974 and assigned to the assignee of the present invention. When pasted with active material and cut into plates, such expanded metal grids frequently have sharp gridwire ends along the lateral edges of the plate which can puncture the borders of the separator envelope which, in turn, can cause internal shorting within the battery and a significant reduction in its useful life.